package hanjia;

public class hanjia20 {
	public static void main (String [] args){
		double fz = 1;
        double fm = 1;
        double fra = fz/fm;
        double sum = 0;
 
        for (int i =1; i<=20; i++){
            double t1 = fz;
            double t2 = fm;
            fz = t1 + t2;
            fm = t1;
            fra = fz / fm;
            sum += fra;
 
        }
        System.out.println(sum);
	}
}
